BOSTON — RELIGIOUS missionaries once considered the Japanese language to be the work of Satan, the devil's language, created in hell and made inhumanly difficult to learn in order to frustrate their preaching. Today, however, despite its ominous reputation, record numbers of United States students are enrolling in Japanese classes with the hope of landing high-paying jobs when they graduate.In the past decade, the number of students at two- and four-year colleges enrolled in Japanese language programs has seen more than a four-fold increase, from 11,506 in 1980 to 45,717 in 1990, according to the Modern Language Association in New York. But the US track record with foreign languages is a poor one, and even those languages similar to English, such as French or Spanish, remain a mystery to many Americans who sat through countless hours of high school classes. Japanese is far from similar. Compared with English, sentences are longer and are said backward; personal pronouns are almost nonexistent; subjects, and sometimes even verbs, are omitted; and the slightest mispronunciation can be the difference between saying that you were woken and that you were raped, between introducing yourself as someone's adviser and announcing that you are their anus. These difficulties notwithstanding, today's students seem to be faring far better than their parents did. m always amazed at how well they do," says Prof. Kiyoko Morita of Wellesley College in Wellesley, Mass. "When I see how quickly they pick it up, I think to myself that the Japanese people had better watch out, economically and in business." Prof. Kazuko Ozawa of Harvard University agrees. "They're doing very well. For many of them, after studying three or four years they're at a point where they can go over to Japan and begin to make good progress." The implication is clear: Those who intend to use it professionally must expect to put in some time in Japan before considering themselves proficient. The reason for this may be that the culture is so different from that of the US. Vocabulary and grammatical patterns can be memorized, but cultural aspects of the society that are manifest in the language are far too complicated to be taught in a classroom. Japanese is a situational language and the way something is said differs with the relationship between speaker, listener, or the person about whom they are speaking; their respective families, ages, professional statuses, and companies all affect the way they express themselves. In this respect, Japanese isn't one language but a group of them, changing with a dizzying array of social conventions with which Americans have no experience. Japanese people are raised dealing with the shifting concepts of in group/out group, male and female speech patterns, appropriate politeness levels, and humble and honorific forms of speech. An unwary student, armed only with a few years of classroom Japanese, can pile up mistakes in this regard very quickly. Because of these difficulties, few students sign up for the language simply to fill out their schedules, and the majority of those studying the language intend to use it professionally. But despite the allure of the Japanese market for US companies, so far, few of them seem interested in hiring Japanese-speaking Americans. The best a typical liberal arts major with a Japanese background can hope for is to be hired over candidates for whom all other things are equal. "American companies still don't seem eager to hire someone just because he knows Japanese," says Carl Kay, president of the Boston-based translating company, Japan Language Services. "They just aren't sure what to do with them." The job market with Japanese companies is slightly better but still less than would be expected. The situation is very different for students who have a second skill, in addition to Japanese. Kathleen Schaeffer of the Japan program at the Massachusetts Institute of Technology in Cambridge, Mass., says, "Students who combine Japanese with something else, such as a law degree, an MBA, or some form of technical expertise, enter the job market with a powerful combination." Toward this end, some colleges, mos t notably MIT, offer technical Japanese classes to this level of student. So, while the job market for Japanese-speaking graduates remains weak, the language's reputation as the devil's language may be on its way out. "It's a long gone myth," laughs Professor Morita. "Before, the Japanese teachers themselves had bad attitudes. They thought the language was difficult and they passed that feeling on to their students. It's not that they did a bad job but they had no experience teaching. They were mostly housewives. But nowadays there are so many trained, experienced teachers that the situation is different. And Americans are not inept at learning languages so they shouldn't be afraid to tackle this." With this in mind, her advice to prospective students is simple. "Just go for it," she smiles.